1qt per pound of grain is a little on the thick side. 1.25-1.3qt is a little more typical.
it sounds like you just need the right kind of thermometer for the job. something that doesn't need to be inserted too deep to get a good reading.
I like instant read kitchen thermometers, like what the food service industry uses.
the lab thermo changes because water often is not a consistent temperature. if you read up on fluid thermodynamics it'll shed some light as to why water temperatures get stratified.
Primary: English Mild
On tap: Pale Ale, Lancelot's Wheat, English Brown Ale, Steam Beer, HoovNuts IPA
Bottled: MOAM, Braggot, Raspberry Melomel, Merlot, Apfelwein, Pyment, Sweet mead, Cabernet
Gal in 2009: 27, Gal in 2010: 34, Gal in 2011: 13, Gal in 2012: 10